Why is the LatestMeasure function returning empty values?

Weight.swift

//
//  Weight.swift
//  Vekt
//
//  Created by Hidde van der Ploeg on 26/09/2016.
//  Copyright © 2016 Hidde van der Ploeg. All rights reserved.
//

import UIKit
import HealthKit

private let getWeight = HKQuantityType.quantityType(forIdentifier: HKQuantityTypeIdentifier.bodyMass)

let healthKitStore:HKHealthStore = HKHealthStore()
let healthKitManager: HealthKitManager = HealthKitManager()

let weightQuery = HKSampleQuery( sampleType: getWeight!, predicate: nil, limit: 999, sortDescriptors: nil, resultsHandler: { (sampleQuery, results, error ) -> Void in
    
    if let queryError = error {
        return
    }} )


struct Weight {
    var weight : String
    var unit : String
    var date : String?
    
    init(_ weight: String, unit: String, date: String?){
        
        self.weight = weight
        self.unit = unit
        self.date = date
    }
}

var current = Weight("", unit: "", date: "")

func isStorePossible() {
    healthKitManager.setupHealthStoreIfPossible { (success, error) -> Void in
        if error == nil {
            // health kit was setup successfully
        } else {
            print("Error occured while setting up Health Kit: \(error!.localizedDescription)")
        }
    }
}


func latestMeasure() -> Weight? {
    var latestWeight: Weight?
    
    isStorePossible()

    healthKitManager.readMostRecentSample(getWeight!, completion: { (mostRecentWeight, error) -> Void in
        
        if (error != nil) {
            print("Error reading weight from HealthKit Store: \(error?.localizedDescription)")
            return;
        }
        var weightLocalizedString = ""
        
        let dateFormatter = DateFormatter()
        dateFormatter.dateFormat = "yyyy-MM-dd"
        dateFormatter.dateStyle = .medium
        dateFormatter.timeStyle = .short
        let date = dateFormatter.string(from: (mostRecentWeight?.endDate)!)
        
        let weight = mostRecentWeight as? HKQuantitySample;
        if let kilograms = weight?.quantity.doubleValue(for: HKUnit.gramUnit(with: .kilo)) {
            let weightFormatter = MassFormatter()
            weightFormatter.isForPersonMassUse = true;
            weightLocalizedString = weightFormatter.string(fromKilograms: kilograms)
        }
        
        let fullAmount = weightLocalizedString.characters.split{$0 == " "}.map(String.init)
        let amount =  fullAmount[0]
        let unit = fullAmount[1]
        latestWeight = Weight(amount, unit: unit, date: date)
    })
    return latestWeight
}